1. Field of the Invention
The present invention relates to a drawing apparatus, and a method of manufacturing an article.
2. Description of the Related Art
A drawing apparatus using a charged particle beam such as an electron beam performs overlay drawing that draws a new pattern overlaid on a pattern (to be referred to as a “shot pattern” hereinafter) formed in each shot region of a substrate (see Japanese Patent Laid-Open No. S62-144323).
In the overlay drawing, first, a substrate is moved based on the designed array coordinate values of a plurality of shot patterns, and positions when some of the plurality of shot patterns are aligned to a reference position are actually measured. Next, assuming the designed array coordinate values of shot patterns and actual array coordinate values to align have a unique relation including a predetermined error, error parameters are decided such that the average deviation between the plurality of measured values and the actual array coordinate values to align is minimized. The actual array coordinate values of the shot patterns are obtained based on the error parameters and the designed array coordinate values of the shot patterns. The substrate is positioned in accordance with the actual array coordinate values, and a new pattern is drawn.
In such overlay drawing, distortions (for example, expansion/contraction and rotation) of shot patterns are also measured as well as the actual array coordinate values of the shot patterns. The distortions of shot patterns occur due to factors of a lithography apparatus such as a drawing apparatus when forming a pattern or due to deformation of a substrate caused by a heat process when forming a pattern.
FIG. 5A is a view showing the array of 5 (rows)×5 (columns) shot patterns formed on a substrate SB. Actual shot patterns SP are indicated by solid lines, and designed shot patterns SP′ are indicated by broken lines. FIG. 5B shows a state in which overlay drawing is performed for the substrate SB (actual shot patterns SP) by a drawing apparatus including a plurality of charged particle optical systems CP1, CP2, and CP3. Referring to FIG. 5B, each of the charged particle optical systems CP1 to CP3 emits 5 (rows)×5 (columns) charged particle beams to the substrate SB. When a stage that holds the substrate SB is moved to the upper side with respect to the charged particle optical systems CP1, CP2, and CP3, the charged particle optical systems CP1, CP2, and CP3 draw stripe regions S1, S2, and S3, respectively (stripe drawing). In this stripe drawing, multiple irradiation is performed for the same positions of the substrate by the charged particle beams of the charged particle optical systems which are arrayed in the substrate moving direction. The irradiation is on/off-controlled, thereby controlling the irradiating doses of the charged particle beams on the substrate.
Each charged particle optical system includes a deflector configured to deflect charged particle beams. This deflector adjusts the positions of (drawing regions defined by) a plurality of charged particle beams on the substrate at once. In the stripe drawing, a new pattern is overlaid and drawn on the shot patterns while adjusting the positions of the drawing regions of the charged particle optical systems by the deflectors based on the actual positions of the shot patterns on the substrate.
In overlay drawing, however, when the drawing region of a charged particle optical system extends over shot patterns adjacent in the substrate moving direction (that is, located on both of two adjacent shot patterns), the following problem arises. In fact, the shot patterns on the substrate are not always periodically arrayed along the designed array coordinates (that is, the positions of the shot patterns are shifted). It is therefore necessary to perform drawing while adjusting (correcting) the position of the drawing region with respect to the shot patterns. However, when the drawing region of a charged particle optical system extends over shot patterns adjacent in the substrate moving direction, the position of the drawing region of the charged particle optical system can be corrected with respect to only one of the shot patterns. Hence, before drawing for a preceding shot pattern is completed, drawing for the next shot pattern cannot be performed. For this reason, after drawing for a preceding shot pattern is completed, the substrate needs to be moved in an opposite direction by a distance corresponding to the charged particle beams arrayed in the substrate moving direction (a length along the substrate moving direction in the drawing region) to perform drawing for the next shot pattern. As a result, since the stage that holds the substrate is discontinuously moved (that is, the stage cannot continuously be moved in one direction), stage movement takes time, and the throughput lowers. In addition, since stage movement is complex, the reproducibility of stage position control lowers, and the precision of relative alignment between the charged particle beams and the substrate also lowers.